The present invention relates to disc magnetic recording systems, and in particular to suspension systems for carrying a magnetic recording head in close following relation to the surface of a rotating magnetic recording disc.
Data storage and retrieval in disc magnetic recording systems are accomplished through a magnetic recording head suspended in close following relation to the surface of a rotating magnetic recording disc. The recording head is essentially a transducer assembly that, in a storage mode, is used to write digital information in the form of encoded magnetic flux transitions on the surface of a recording disc, or, in a retrieval mode, is used to read the recorded flux transitions to recover the information. The recording head may be fixed over a particular one of the concentric recording tracks on the recording disc (the "fixed head" system), or may be translatable from track to track (the "head protract" system).
In most current systems, the recording head(s) is(are) not normally retracted from the disc surface. That is, prior to start-up, a recording head is in physical contact with a stationary disc surface; as the disc commences rotation during start-up the recording head "takes-off" from the disc surface, thereafter flying at a predetermned flying height, typically on the order of tens of microinches. When the system is shutdown, the recording head again "lands" on the disc surface as the disc ceases rotating.
Current recording heads are designed not only for their transducer (input/output) characteristics, but also for their aerodynamic properties. Head bearing elements define air bearing surfaces which are aerodynamically designed to provide the lift and stability necessary for the recording head to fly over the disc surface. Since the transducer characteristics of a recording head depend, in part, upon its flying height, careful attention is paid to the two design factors that determine flying height: (a) the configuration and total surface of the air bearing surfaces, and (b) the load supplied to the recording head.
The load on a recording head is supplied by the head suspension assembly. Thus, the suspension assembly performs two important functions: (a) carrying the recording head in close following relation to the disc surface, and (b) supplying a constant magnitude load to the recording head to maintain a predetermined flying height. Additionally, the suspension assembly must permit the recording head some degree of pitch, roll and transverse (i.e., perpendicular to the disc surface) movement to accommodate unavoidable aerodynamic instabilities, while at the same time counteracting or dampening these motions to reduce the liklihood of head-disc dynamic contact (head crash).
Head suspension assemblies commonly use a gimbal mounting arrangement to accommodate pitch, roll and transverse head movements. To provide the necessary load force on the recording head, one common technique is to incorporate into the suspension assembly a thin flange or tongue of stainless steel that functions essentially as a load spring. The load tongue is bent by a precisely controlled amount and then heated; when the load tongue cools it retains its bent configuration, establishing the loading (i.e., spring force) that the suspension assembly will provide. Head load is supplied to a recording head mounted to the suspension assembly by counter-deflecting the load tongue and attaching a substantially straight, cantilevered head contact arm such that the free end of the contact arm contacts the suspension assembly adjacent the recording head. During operation, the contact arm maintains the counter-deflection of the load tongue and transmits the resulting load to the recording head.
The above technique for supplying a load to a recording head is disadvantageous. As noted previously, to accurately maintain a predetermined flying height, the head load magnitude must be precisely controlled. Accordingly, the heat-relax bending of the load tongue must be performed within narrow tolerances. Such tolerances have proved difficult to achieve; often the load tongue bending must be adjusted after the recording head is mounted to the suspension assembly, causing production delays and increased production costs.
A general object of the present invention is to provide an improved suspension assembly for carrying a magnetic recording head, and supplying a predetermined head load. A specific object is to provide a suspension assembly incorporating an head loading arrangement that can be accurately, reliably and economically fabricated and assembled such that head load magnitude can be established without post-assembly adjustment.